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Pests & Wildlife

Pests & Wildlife

Yellow Jackets

Commonly mistaken for bees, the term yellow jacket refers to a number of different species of wasps. Included in this group of ground-nesting species is the western yellow jacket. This is the most commonly encountered species and is also known as the “meat bee”. This wasp tends to be medium sized and black with jagged bands of bright yellow or white on the abdomen. They have a very short and narrow “waist” -the area where the thorax attaches to the abdomen. There are seven other species that are common in rotted tree stumps at higher elevations.

Prevention

 
The best way to prevent unpleasant encounters with social wasps is to avoid them. If you know where they are try not to go near their nesting places. Wasps can become very defensive when their nest is disturbed. Be on the lookout for nests when outdoors. Wasps that are flying directly in and out of a single location are probably flying to and from their nest.
 
Scavenging wasps usually won’t become a problem if there is no food around to attract them. When nuisance wasps are present outdoors, keep foods including pet food and drinks covered or inside the house. Also keep garbage in tightly sealed garbage cans. Once wasps discover food they will continue to hunt around that location long after the source has been removed.
 
If wasp nests must be eliminated, it is easiest and safest to call for professional help. We exterminate wasps in Portland, Beaverton, Tigard, Wilsonville, Tualatin, Gresham, Hillsboro, and Vancouver.

Behavior

 

Life Cycle

Yellow jackets commonly build nests in rodent burrows, but they also select other protected cavities such as voids in the walls and ceilings of houses. Colonies that begin each spring, by a single reproductive female, can reach populations of between 1,500 and 15,000 individuals, depending on the species. The wasps build a nest of paper made from a mixture of saliva and fibers scraped from wood. It is built as multiple tiers of vertical cells that are similar to nests of paper wasps but enclosed by a paper envelope around the outside. It usually contains a single entrance hole. If a hole isn’t spacious enough, yellow jackets will increase the size by moistening the soil and digging. Similar behavior inside a house sometimes leads to a wet patch that develops into a hole in a wall or ceiling. 

 

Immature yellow jackets are white, grub like, larvae that become white pupae. The pupae develop their adult coloring just before they emerge as adult wasps. Immatures normally aren’t seen unless the nest is torn open or a sudden loss of adult caretakers leads to an exodus of starving larvae.

 

Aerial-nesting yellow jackets build paper nests that they attach to the eaves of a building or hang from the limb of a tree. The entrance is typically a hole at the bottom of the nest. These aerial nesters don’t become scavengers at the end of the season, but they are extremely defensive when their nests are disturbed. Defending wasps sometimes bite and/or sting simultaneously. Wasp stingers have no barbs and can be used repeatedly, especially when the wasp gets inside clothing. As with any stinging incident, it is best to leave the area of the nest site as quickly as possible.

 

Environmental Impact

Most social wasps provide an extremely beneficial service by eliminating large numbers of other pest insects through predation and should be protected and encouraged to nest in areas where there is little human or animal activity. Although many animals prey on social wasps including birds, reptiles, amphibians, skunks, bears, raccoons, spiders, preying mantas, and bald-faced hornets-none of these provide satisfactory biological control in home situations.
 

Injury and Damage

Concern about yellow jackets is based on their persistent, pugnacious behavior around food sources and their aggressive defense of their colony. Stinging behavior is usually encountered at nesting sites, but scavenging yellow jackets sometimes will sting if someone tries to swat them away from a potential food source. When scavenging at picnics or other outdoor meals, wasps will crawl into soda cans and can sting your lips or the inside of your mouth or throat.